Hydrogen generating apparatus and fuel cell power generation system controlling amount of hydrogen generation

ABSTRACT

Hydrogen generating apparatus that is capable of controlling the amount of hydrogen generation. The hydrogen generating apparatus has an electrolyzer, a first electrode, a second electrode, a switch, which is located between the first electrode and the second electrode, a flow rate meter, which measures an amount of hydrogen generation in the second electrode, and a switch controller, which receives a set value, compares the amount of hydrogen generation measured by the flow rate meter with the set value, and controls an on/off status of the switch. The amount of hydrogen generation can be controlled by use of on/off time and/or on/of frequency of the switch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/812,656, filed on Jun. 20, 2007 now U.S. Pat. No. 7,879,205.And this application claims the benefit of Korean Patent Application No.10-2007-0017343 filed with the Korean Intellectual Property Office onFeb. 21, 2007, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrogen generating apparatus, moreparticularly to a hydrogen generating apparatus that can control theamount of generation of hydrogen supplied to a fuel cell.

2. Background Art

A fuel cell refers to an energy conversion apparatus that directlyconverts chemical energy of a fuel (hydrogen, LNG, LPG, methanol, etc.)and air to electricity and/or heat by means of an electrochemicalreaction. Unlike a conventional power generation technology thatrequires fuel combustion, steam generation, or a turbine or powergenerator, the fuel cell technology needs no combustion process ordriving device, thereby boosting energy efficiency and curbingenvironmental problems.

FIG. 1 illustrates an operational architecture of a fuel cell.

Referring to FIG. 1, a fuel cell 100 is composed of an anode as a fuelpole 110 and a cathode as an air pole 130. The fuel pole 110 is providedwith hydrogen molecules (H₂), and decomposes them into hydrogen ions(H⁺) and electrons (e⁻). The hydrogen ion (H⁺) moves toward the air pole130 via a membrane 120, which is an electrolyte layer. The electronmoves through an external circuit 140 to generate an electric current.In the air pole 130, the hydrogen ions and the electrons are combinedwith oxygen molecules in the atmosphere, generating water molecules. Thefollowing chemical formulas represent the above chemical reactionsoccurring in the fuel cell 100.Fuel pole 110: H₂

2H⁺+2e ⁻Air pole 130: ½O₂+2H⁺+2e ⁻

H₂0Overall reaction: H₂+½O₂

H₂0  CHEMICAL FORMULA 1

In short, the fuel cell 100 functions as a battery by supplying theelectric current, generated due to the flowing of the decomposedelectrons, to the external circuit 140. Such a fuel cell 100 hardlyemits an atmospheric pollutant such as Sox and NOx and makes littlenoise and vibration.

Meanwhile, in order to produce electrons in the fuel pole 110, the fuelcell 100 necessitates a hydrogen generating apparatus that can change acommon fuel to hydrogen gas.

A hydrogen storage tank, generally known as a hydrogen generatingapparatus, however, occupies a large space and should be kept with care.

Moreover, as a portable electronic device, such as a mobile phone and anotebook computer, requires a large capacity of power, it is necessarythat the fuel cell have a large capacity and perform high performancewhile it is small.

In order to meet the above needs, methanol or formic acid, permitted tobe brought into an airplane by International Civil Aviation Organization(ICAO), is used for fuel reforming, or methanol, ethanol, or formic acidis directly used as a fuel for the fuel cell.

However, the former case requires a high reforming temperature, has acomplicated system, consumes driving power, and contains impurities(e.g., CO₂ and CO) in addition to pure hydrogen. The latter casedeteriorates power density due to a low rate of a chemical reaction inthe anode and a cross-over of hydrocarbon through the membrane.

SUMMARY OF THE INVENTION

The present invention provides a hydrogen generating apparatus, a fuelcell power generation system, a method of controlling the quantity ofhydrogen generation, and a recorded medium recorded with a programperforming the method that can generate pure hydrogen at roomtemperature through an electrochemical reaction.

The present invention also provides a hydrogen generating apparatus, afuel cell power generation system, a method of controlling the quantityof hydrogen generation, and a recorded medium recorded with a programperforming the method that can control the quantity of hydrogengeneration without a separate BOP (Balance of Plant) unit whilemaintaining a simple structure.

The present invention also provides a hydrogen generating apparatus, afuel cell power generation system, a method of controlling the quantityof hydrogen generation, and a recorded medium recorded with a programperforming the method that are economical and eco-friendly.

The present invention also provides a hydrogen generating apparatus, afuel cell power generation system, a method of controlling the quantityof hydrogen generation, and a recorded medium recorded with a programperforming the method that can control the quantity of hydrogengeneration by use of On/Off time and/or On/Off frequency of a switch.

Moreover, the present invention provides a hydrogen generatingapparatus, a fuel cell power generation system, a method of controllingthe quantity of hydrogen generation, and a recorded medium recorded witha program performing the method that can prevent waste or risk ofleaking surplus hydrogen in the air simply by turning on the switch andreduce the noise and power consumption by not using a gas pump or aliquid pump.

Moreover, the present invention provides a hydrogen generating apparatusthat can control the amount of generation by use of feedback controlaccording to the demand from a load connected to the fuel cell.

An aspect of the present invention features a hydrogen generatingapparatus that is capable of controlling the amount of hydrogengeneration.

The hydrogen generating apparatus in accordance with an embodiment ofthe present invention includes an electrolyzer, which is filled with anaqueous electrolyte solution containing hydrogen ions, a firstelectrode, which is accommodated in the electrolyzer, is submerged inthe aqueous electrolyte solution, and generates electrons, a secondelectrode, which is accommodated in the electrolyzer, is submerged inthe aqueous electrolyte solution, and receives the electrons to generatehydrogen, a switch, which is located between the first electrode and thesecond electrode, a flow rate meter, which measures an amount ofhydrogen generation in the second electrode, and a switch controller,which receives a set value, compares the amount of hydrogen generationmeasured by the flow rate meter with the set value, and controls anon/off status of the switch.

The switch controller can be inputted with the set value directly from auser through an input device. The hydrogen generating apparatus can becoupled to a fuel cell and supplies hydrogen, and the switch controllercan be inputted with the set value in accordance with an amount ofhydrogen generation that is required by the fuel cell.

The metal forming the first electrode can have a higher ionizationtendency than a metal forming the second electrode.

The flow rate meter can measure the amount of hydrogen generation inunits of flowrate. The switch controller can generate and output aswitch control signal turning the switch on and off, and the switchcontroller can determine an on/off ratio of the switch within one cycleby varying a duty ratio of the switch control signal.

The switch controller can control a fluctuation in the amount ofhydrogen generation by varying an on/off frequency of the switch controlsignal. The switch controller can compare the set value with themeasured amount of hydrogen generation, and can increase the duty ratioif the amount of hydrogen generation is smaller than the set value,reduce the duty ratio if the amount of hydrogen generation is greaterthan the set value, and maintain the duty ratio if the amount ofhydrogen generation is equal to the set value. The set value includes anupper limit and a lower limit, and the switch controller can compare theset value with the measured amount of hydrogen generation, and canincrease the duty ratio if the amount of hydrogen generation is smallerthan the lower limit, reduce the duty ratio if the amount of hydrogengeneration is greater than the upper limit, and maintain the duty ratioif the amount of hydrogen generation is between the lower limit and theupper limit.

Another aspect of the present invention features a fuel cell powergeneration system including a hydrogen generating apparatus that iscapable of controlling the amount of hydrogen generation.

The fuel cell power generation system in accordance with an embodimentof the present invention has a hydrogen generating apparatus, whichcontrols an amount of hydrogen generation by controlling an on/offstatus of a switch connected between electrodes, a fuel cell, which issupplied with hydrogen generated by the hydrogen generating apparatusand produces a direct current by converting chemical energy of thehydrogen to electrical energy, and a load, which is provided theelectric energy and performing a predetermined operation.

The hydrogen generating apparatus can include an electrolyzer, which isfilled with an aqueous electrolyte solution containing hydrogen ions, afirst electrode, which is accommodated in the electrolyzer, is submergedin the aqueous electrolyte solution, and generates electrons, a secondelectrode, which is accommodated in the electrolyzer, is submerged inthe aqueous electrolyte solution, and receives the electrons to generatehydrogen, a switch, which is located between the first electrode and thesecond electrode, a switch controller, which received a demanded powerfrom the load, measuring an output of the fuel cell, compares thedemanded power with the output, and controls an on/off status of theswitch. The metal forming the first electrode can have a higherionization tendency than a metal forming the second electrode.

The switch controller can generate and output a switch control signalturning the switch on and off, and the switch controller can determinean on/off ratio of the switch within one cycle by varying a duty ratioof the switch control signal. The switch controller can control afluctuation in the amount of hydrogen generation by varying an on/offfrequency of the switch control signal. The switch controller cancompare the demanded power with the output, and can reduce the dutyratio if the output is greater than the demanded power, increase theduty ratio if the output is smaller than the demanded power, andmaintain the duty ratio if the output is equal to the demanded power.

The fuel cell power generation system in accordance with an embodimentof the present invention further comprises a rechargeable battery, beingcoupled between the fuel cell and the load, being charged by theelectric energy from the fuel cell, and providing the charged electricenergy when the load needs.

The hydrogen generating apparatus can include an electrolyzer, which isfilled with an aqueous electrolyte solution containing hydrogen ions, afirst electrode, which is accommodated in the electrolyzer, submerged inthe aqueous electrolyte solution, and generating electrons, a secondelectrode, which is accommodated in the electrolyzer, submerged in theaqueous electrolyte solution, receiving the electrons to generatehydrogen, a switch, which is located between the first electrode and thesecond electrode, a switch controller, which measures present voltage ofthe rechargeable battery, compares a fully-charged voltage with thepresent voltage, and controlling an on/off status of the switch. Themetal forming the first electrode can have a higher ionization tendencythan a metal forming the second electrode.

The switch controller generates and outputs a switch control signalturning the switch on and off, and the switch controller determines anon/off ratio of the switch within one cycle by varying a duty ratio ofthe switch control signal. And the switch controller controls afluctuation in the amount of hydrogen generation by varying an on/offfrequency of the switch control signal.

The switch controller compares the present voltage with thefully-charged voltage, and increases the duty ratio if the presentvoltage is smaller than the fully-charged voltage, and minimizes theduty ratio if the present voltage is equal to or greater than thefully-charged voltage.

The meter can be an output meter that measures an output of the fuelcell in units of watt (W), volt (V), ampere (A), ohm (Ω) and acombination thereof. The switch controller can control a fluctuation inthe output of the fuel cell by varying an on/off frequency of the switchcontrol signal. The switch controller can compare the set value with themeasured output of the fuel cell, and can increase the duty ratio if theoutput of the fuel cell is smaller than the set value, reduce the dutyratio if the output of the fuel cell is greater than the set value, andmaintain the duty ratio if the output of the fuel cell is equal to theset value. The set value can include an upper limit and a lower limit,and the switch controller can compare the set value with the measuredoutput of the fuel cell, and can increase the duty ratio if the outputof the fuel cell is smaller than the lower limit, reduce the duty ratioif the output of the fuel cell is greater than the upper limit, andmaintain the duty ratio if the output of the fuel cell is between thelower limit and the upper limit.

Another aspect of the present invention features a method of controllingan amount of hydrogen generation in a hydrogen generating apparatuscontrolling an amount of hydrogen generation by controlling an on/offstatus of a switch located between electrodes.

The method of controlling an amount of hydrogen generation in accordancewith an embodiment of the present invention includes the steps of beinginputted with a set value; comparing a measured amount of hydrogengeneration and the set value; and increasing a duty ratio of a switchcontrol signal if the amount of hydrogen generation is smaller than theset value, reducing the duty ratio of the switch control signal if theamount of hydrogen generation is greater than the set value, andmaintaining the duty ratio of the switch control signal if the amount ofhydrogen generation is equal to the set value, in which the switchcontrol signal controls the on/off status of the switch within one cyclein accordance with the duty ratio.

The method of controlling an amount of hydrogen generation in accordancewith another embodiment of the present invention includes the steps ofbeing inputted with an upper value and a lower value; comparing ameasured amount of hydrogen generation with the upper value and thelower value; and increasing a duty ratio of a switch control signal ifthe amount of hydrogen generation is smaller than the lower value,reducing the duty ratio of the switch control signal if the amount ofhydrogen generation is greater than the upper value, and maintaining theduty ratio of the switch control signal if the amount of hydrogengeneration is between the lower value and the upper value, in which theswitch control signal controls the on/off status of the switch withinone cycle in accordance with the duty ratio.

The method of controlling an amount of hydrogen generation in accordancewith another embodiment of the present invention, which is controllingan amount of hydrogen generation by controlling an on/off status of aswitch located between electrodes, measures an output of the fuel cell,and receiving a demanded power from the load, compares the output withthe demanded power, and reduces a duty ratio of switch control signal ifthe output is greater than the demanded power, increasing the duty ratioof switch control signal if the output is smaller than the demandedpower, and maintains the duty ratio of switch control signal if theoutput is equal to the demanded power, in which the switch controlsignal controls the on/off status of the switch within one cycle inaccordance with the duty ratio.

The method of controlling an amount of hydrogen generation in accordancewith another embodiment of the present invention, which is controllingan amount of hydrogen generation by controlling an on/off status of aswitch located between electrodes, measures a present voltage of therechargeable battery, compares the present voltage with a fully-chargedvoltage, and increasing a duty ratio of switch control signal if thepresent voltage is smaller than the fully-charged voltage, and minimizesthe duty ratio of switch control signal if the present voltage is equalto or greater than the fully-charged voltage, in which the switchcontrol signal controls the on/off status of the switch within one cyclein accordance with the duty ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims and accompanying drawings where:

FIG. 1 illustrates an operational architecture of a fuel cell;

FIG. 2 shows a sectional view of a hydrogen generating apparatus inaccordance with an embodiment of the present invention;

FIG. 3 is a graph showing the power consumption of mobile phone.

FIG. 4 is a graph showing how the amount of electric current between afirst electrode and a second electrode and the amount of generatedhydrogen are related in a hydrogen generating apparatus in accordancewith an embodiment of the present invention;

FIG. 5 shows a block diagram of a control unit of a hydrogen generatingapparatus in accordance with an embodiment of the present invention;

FIG. 6 shows a block diagram of a fuel cell power generation system inaccordance with another embodiment of the present invention;

FIG. 7 is a block diagram of a fuel cell power generation system inaccordance with another embodiment of the present invention.

FIG. 8 shows a graph of the amount of hydrogen generation, expressed inunits of flow rate, when the switch is turned on;

FIG. 9 shows a first example of the on/off frequency of the switch of ahydrogen generating apparatus in accordance with an embodiment of thepresent invention;

FIG. 10 shows a second example of the on/off frequency of the switch ofa hydrogen generating apparatus in accordance with an embodiment of thepresent invention;

FIG. 11 shows how the amount of hydrogen generation is related to timewhen the on/off frequency of the switch is controlled.

FIG. 12 shows a first example of duty ratios of the switch of a hydrogengenerating apparatus in accordance with an embodiment of the presentinvention;

FIG. 13 shows a second example of duty ratios of the switch of ahydrogen generating apparatus in accordance with an embodiment of thepresent invention;

FIG. 14 shows how the quantity of hydrogen generation is related to timewhen the duty ratio of the switch is controlled.

FIG. 15 shows a flowchart of a method of controlling the quantity ofhydrogen generation in a hydrogen generating apparatus in accordancewith an embodiment of the present invention;

FIG. 16 shows a flowchart of a method of controlling the quantity ofhydrogen generation in a hydrogen generating apparatus in accordancewith another embodiment of the present invention; and

FIG. 17 shows a flowchart of a method of controlling the quantity ofhydrogen generation in a hydrogen generating apparatus in accordancewith another embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Since there can be a variety of permutations and embodiments of thepresent invention, certain embodiments will be illustrated and describedwith reference to the accompanying drawings. This, however, is by nomeans to restrict the present invention to certain embodiments, andshall be construed as including all permutations, equivalents andsubstitutes covered by the spirit and scope of the present invention.Throughout the drawings, similar elements are given similar referencenumerals. Throughout the description of the present invention, whendescribing a certain technology is determined to evade the point of thepresent invention, the pertinent detailed description will be omitted.

Terms such as “first” and “second” can be used in describing variouselements, but the above elements shall not be restricted to the aboveterms. The above terms are used only to distinguish one element from theother. For instance, the first element can be named the second element,and vice versa, without departing the scope of claims of the presentinvention. The term “and/or” shall include the combination of aplurality of listed items or any of the plurality of listed items.

When one element is described as being “connected” or “accessed” toanother element, it shall be construed as being connected or accessed tothe other element directly but also as possibly having another elementin between. On the other hand, if one element is described as being“directly connected” or “directly accessed” to another element, it shallbe construed that there is no other element in between.

The terms used in the description are intended to describe certainembodiments only, and shall by no means restrict the present invention.Unless clearly used otherwise, expressions in the singular numberinclude a plural meaning. In the present description, an expression suchas “comprising” or “consisting of” is intended to designate acharacteristic, a number, a step, an operation, an element, a part orcombinations thereof, and shall not be construed to preclude anypresence or possibility of one or more other characteristics, numbers,steps, operations, elements, parts or combinations thereof.

Unless otherwise defined, all terms, including technical terms andscientific terms, used herein have the same meaning as how they aregenerally understood by those of ordinary skill in the art to which theinvention pertains. Any term that is defined in a general dictionaryshall be construed to have the same meaning in the context of therelevant art, and, unless otherwise defined explicitly, shall not beinterpreted to have an idealistic or excessively formalistic meaning.

Hereinafter, certain embodiments will be described in detail withreference to the accompanying drawings. Identical or correspondingelements will be given the same reference numerals, regardless of thefigure number, and any redundant description of the identical orcorresponding elements will not be repeated.

FIG. 2 is a sectional view of a hydrogen generating apparatus inaccordance with an embodiment of the present invention.

A hydrogen generating apparatus 200 includes an electrolyzer 210, afirst electrode 220, a second electrode 230 and a control unit 240. Forthe convenience of description and understanding, it will be presumedbelow that the first electrode 220 is composed of magnesium (Mg) and thesecond electrode 230 is composed of stainless steel.

The electrolyzer 210 is filled with an aqueous electrolyte solution 215.The aqueous electrolyte solution 215 contains hydrogen ions, which areused by the hydrogen generating apparatus 200 to generate hydrogen gas.

Examples of the electrolyte for the aqueous electrolyte solution 215 areLiCl, KCl, NaCl, KNO₃, NaNO₃, CaCl₂, MgCl₂, K₂SO₄, Na₂SO₄, MgSO₄, AgCl,or the like.

The electrolyzer 210 accommodates the first electrode 220 and the secondelectrode 230, the entirety or portions of which are submerged in theelectrolyte solution 215.

The first electrode 220 is an active electrode, where the magnesium (Mg)is oxidized to magnesium ions (Mg²⁺), releasing electrons due to thedifference in ionization energies of magnesium and water. The releasedelectrons move to the second electrode 230 through a first electric wire225, the control unit 240 and a second electric wire 235.

The second electrode 230 is an inactive electrode, where the watermolecules receive the electrons moved from the first electrode 220 andthen are decomposed into the hydrogen molecules.

The above chemical reactions can be represented as the followingchemical formula 2:First electrode 220: Mg

Mg²⁺+2e ⁻Second electrode 230: 2H₂0+2e ⁻

H₂+2(OH)⁻Overall reaction: Mg+2H₂O

Mg(OH)₂+H₂  CHEMICAL FORMULA 2

The reaction rate and the efficiency of the chemical reaction depend onvarious factors, including the area of the first electrode 220 and/orthe second electrode 230, the concentration of the aqueous electrolytesolution 215, the type of the aqueous electrolyte solution 215, thenumber of the first electrode 220 and/or the second electrode 230, themethod of connecting the first electrode 220 and the second electrode230, the electric resistance between the first electrode 220 and thesecond electrode 230.

Changing any of the above factors affects the amount of electric current(that is, the amount of electrons) flowing between the first electrode220 and the second electrode 230, thereby altering the reaction rate ofthe electrochemical reaction shown in CHEMICAL FORMULA 2, which in turnchanges the amount of hydrogen generated in the second electrode 230.

Therefore, the amount of the hydrogen generated in the second electrode230 can be controlled by controlling the amount of the electric currentthat flows between the first electrode 220 and the second electrode 230.Faraday's law explains this as shown in MATHEMATICAL FORMULA 1 below.

      MATHEMATICAL  FORMULA  1 $N_{hydrogen} = \frac{i}{nE}$$N_{hydrogen} = {\frac{i}{2 \times 96485}({mol})}$$V_{hydrogen} = {{\frac{i}{2 \times 96485} \times 60 \times 22400\left( {{ml}/\min} \right)} = {7 \times {i\left( {{ml}/\min} \right)}}}$

Where N_(hydrogen) is the amount of hydrogen generated per second(mol/s), V_(hydrogen) is the volume of hydrogen generated per minute(ml/min), i is the electric current (C/s), n is the number of thereacting electrons, and E is the electron charge per mole (C/mol).

In the case of the above CHEMICAL FORMULA 2, n has a value of 2 sincetwo electrons react at the second electrode 230, and E has a value of−96,485 C/mol.

The volume of hydrogen generated per minute can be calculated bymultiplying the time (60 seconds) and the molar volume of hydrogen(22400 ml) to the amount of hydrogen generated per second.

For example, in the case that the fuel cell is used in a 2 W system, andit is assumed that the fuel cell is running a voltage of 0.6V at roomtemperature and that a hydrogen usage ratio is 60%, it takes 42 ml/molof hydrogen and 6 A of electric current. In the case that the fuel cellis used in a 5 W system, it takes 105 ml/mol of hydrogen and 15 A ofelectric current.

The hydrogen generating apparatus 200 can meet the variable hydrogendemand of the fuel cell connected thereto by controlling the amount ofelectric current flowing through the first electric wire 225, connectedto the first electrode 220, and the second electric wire 235, connectedto the second electrode 230.

However, most of the factors that determine the rate of the hydrogengeneration reaction occurring in the second electrode of the hydrogengenerating apparatus 200, except the electric resistance between thefirst electrode 220 and the second electrode 230, are hardly changeableonce the hydrogen generating apparatus 200 is manufactured.

Therefore, the hydrogen generating apparatus 200 according to thisembodiment of the present invention has the control unit 240 disposedbetween the first electric wire 225 and the second electric wire 235,which connect the first electrode 220 and the second electrode 230, inorder to regulate the electric resistance between the first electrode220 and the second electrode 230.

Thus, the hydrogen generating apparatus 200 controls the electricresistance between the first electrode 220 and the second electrode 230,that is, the amount of the electric current flowing therebetween,thereby generating as much hydrogen as needed by the fuel cell.

The first electrode 220 can be also composed of a metal having arelatively high ionization tendency, such as iron (Fe), aluminum (Al),zinc (Zn), or the like. The second electrode 230 can be also composed ofa metal having a relatively low ionization tendency compared to themetal of the first electrode 220, such as platinum (Pt), aluminum (Al),copper (Cu), gold (Au), silver (Ag), iron (Fe), or the like.

The control unit 240 controls a transfer rate, that is, the amount ofelectric current, at which electrons generated in the first electrode220 are transferred to the second electrode 230.

The control unit 240 receives information on power demanded for loadcoupled to the fuel cell and, according to the information, maintains,or increases or reduces the amount of electrons flowing from the firstelectrode 220 to the second electrode 230.

For example, it will be described with reference to the powerconsumption of mobile phone as shown in FIG. 3. FIG. 3 is a graphshowing the power consumption of mobile phone.

The modes of mobile phone depend on the currently-working key or menuselection, and the power consumption also varies accordingly.

Range 301 indicates the situation of requesting a call by dialing, range302 indicates the situation of waiting a receiver's response withhearing of ring-back tone, range 303 indicates the situation of talkingover mobile phone, range 304 indicates the situation of ending a call,and range 305 indicates the situation of sending a call rate message.Since mobile phone operates different components in each of situations,the power consumption varies frequently as shown in FIG. 3.

Therefore controller 240 receives feedback on power demanded for theload such as mobile phone as shown in FIG. 3, and controls to generatehydrogen as much as being demanded so to provide power enough to theload coupled to the fuel cell.

The hydrogen generating apparatus may further comprise an input devicefor user to manually input the demanded amount of power or hydrogen.

The hydrogen generating apparatus of the present invention can have aplurality of the first electrodes 220 and/or the second electrodes 230.In the case that a plural number of the first electrode 220 and/or thesecond electrode 230 are disposed, it can take a shorter time togenerate the demanded amount of hydrogen since the hydrogen generatingapparatus 200 can generate more hydrogen per unit time.

FIG. 4 is a graph showing how the amount of electric current flowingbetween the first electrode 220 and the second electrode 230 is relatedto the volume of hydrogen generated on the second electrode 230. Here,it should be noted that the volume of hydrogen is shown in flow-ratemeasured per minute, because not the total volume of generated hydrogenbut the flow-rate of hydrogen is significant to a fuel cell.

An experiment for FIG. 3 was conducted under the following conditions:First electrode 220: Magnesium (Mg)Second electrode 230: Stainless steelDistance between the electrodes: 3 mmIngredients and concentration of electrolyte: 30 wt % KClNumber of the electrodes: Magnesium 3 each, Stainless steel 3 eachElectrode connecting method: SerialVolume of aqueous electrolyte solution: 60 cc (excessive condition)Size of the electrode: 24 mm×85 mm×1 mm

The above conditions were used for every graph referred to in describingthe present invention.

FIG. 4 shows a greater flow rate of the hydrogen than a theoreticalvalue based on MATHEMATICAL FORMULA 1, due to an interaction of thethree pairs of electrodes.

Nevertheless, it is verified from FIG. 4 that the flow-rate of hydrogenis correlated with the amount of electric current between the firstelectrode 220 and the second electrode 230. Also, the graph shows analmost linear relation between the flow-rate and the amount of theelectric current, which agrees with the MATHEMATICAL FORMULA 1.

FIG. 5 is a block diagram of the control unit 240 of the hydrogengenerating apparatus in accordance with an embodiment of the presentinvention.

The control unit 240 comprises a flow rate meter 510, a switchcontroller 520 and a switch 530.

The flow rate meter 510 measures the amount of hydrogen, in units offlow rate, generated from the second electrode 230 of the hydrogengenerating apparatus. As described above, in order to use the hydrogengenerating apparatus 200 in accordance with the present invention bycoupling to a fuel cell, a certain amount of hydrogen generation, not atotal quantity of hydrogen generation, should be maintained, and thus itis required that the amount of hydrogen generation be measured in unitsof ml/min. Of course, it is possible to use other measurement units aslong as the unit is capable of measuring the flow rate.

The switch controller 520 is inputted with a set value, which is relatedto the amount of hydrogen generation. The hydrogen generating apparatus200 is disposed with a separate input device (not shown), through whichthe set value can be inputted by the user. The required amount of output(i.e. electric power, voltage, current, impedance, and a combinationthereof) or hydrogen generation may be inputted by a fuel cell that iscoupled to the hydrogen generating apparatus 200. In the latter case,the fuel cell may be separately equipped with a hydrogen requiring unitfor inputting the amount of output or hydrogen generation that is neededby the hydrogen generating apparatus 200.

The switch controller 520 compares the inputted set value with theamount of hydrogen generation measured by the flow rate meter 510. Ifthe amount of generated hydrogen is smaller than the set value, theswitch 530 is controlled to increase the amount of hydrogen generation,and if the amount of generated hydrogen is greater than the set value,the switch 530 is controlled to reduce the amount of hydrogengeneration. It is assumed that the switch 530 is controlled by a switchcontrol signal such that the switch controller 520 can turn the switch530 on or off.

The switch is disposed between the first electrode 220 and the secondelectrode 230. Electrons generated in the first electrode 220 istransferred to the second electrode 230 if the switch 530 is turned on,and the electrons generated in the first electrode 220 is nottransferred to the second electrode 230 if the switch 530 is turned off.

That is, the control unit 240 controls the amount of hydrogengeneration, using the switch 530 to control whether the electrons are tobe transferred from the first electrode 220 to the second electrode 230.

FIG. 6 is a fuel cell power generation system comprising controller 240of hydrogen generating apparatus 200, fuel cell coupled thereto, and aload in accordance with another embodiment of the present invention.

The control unit 240 includes a switch controller 610 and a switch 530.Here, the switch controller 610 and the switch 530 function the same wayas described earlier with reference to FIG. 5, and thus theirdescription will be omitted.

The switch controller 610 is coupled to the load 620 to where the fuelcell 100 provides power to. As described above, load 620 demandsdifferent power depending on the currently-working condition (withreference to FIG. 3). Therefore the switch controller 610 receives ademanded power for the currently-working condition of load 620.

And, the switch controller 610 is coupled to the fuel cell 100 toreceive an output of the fuel cell 100. The output of fuel cell 100 is,for example, power being provided to the load 620 by the fuel cell 100that receives hydrogen from the hydrogen generating apparatus 200. Asdescribed above, in order to use the hydrogen generating apparatus 200in accordance with the present invention by coupling to a fuel cell, acertain amount of hydrogen generation, not a total quantity of hydrogengeneration, should be maintained, and thus electric power of the fuelcell 100 based on the amount of hydrogen generation is received in unitsof watt (W). In addition switch controller 610 measures voltage of fuelcell 100 and converts into electric power by use of resistance. Ofcourse, it is possible to use other measurement units as long as theunit is capable of measuring the electric power.

The switch controller 610 compares the output of fuel cell 100 with thedemanded power of load 620. In case the output of fuel cell 100 issmaller than the demanded power, the switch controller 610 changeson/off time of switch 530 to increase the amount of hydrogen generation,and in case the output of fuel cell 100 is greater than the demandedpower, the switch controller 610 changes on/off time of switch 520 toreduce the amount of hydrogen generation. In case the output of fuelcell 100 is within a certain error range compared with the demandedpower, current amount of hydrogen generation is maintained. It isassumed that this switching operation is made by a switch control signalenabling the switch controller 610 to set on/off time of the switch 530.

FIG. 7 is a fuel cell power generation system comprising controller 240of hydrogen generating apparatus 200, fuel cell coupled thereto, and aload in accordance with still another embodiment of the presentinvention.

The control unit 240 includes a switch controller 710 and a switch 530.Here, the switch 530 functions the same way as described earlier withreference to FIG. 5, and thus repetitive description will be omitted.

When compared with the fuel cell power generation system as shown inFIG. 6, the fuel cell power generation system in FIG. 7 furthercomprises a rechargeable battery 700. Since fuel cell has slowresponsiveness, it is not possible to instantaneously respond to a peakpower from the load 620. Thus it becomes possible to respond to peakpower by charging the rechargeable battery 700 in advance.

The switch controller 710 measures voltage of rechargeable battery 700to continuously generate hydrogen for the rechargeable battery 700 to befully charged and for fuel cell 100 to keep providing voltage.

And the switch controller 710 provides the charged voltage ofrechargeable battery 700, and thus in case the voltage of rechargeablebattery 700 drops, makes the hydrogen generating apparatus 200 togenerate hydrogen.

Namely, the switch controller 710 compares present voltage of therechargeable battery 700 with fully-charged voltage. The fully-chargedvoltage means the voltage at when the rechargeable battery 700 is fullycharged. In case the present voltage is smaller than the fully-chargedvoltage, then on/off time of switch 530 is changed to increase theamount of hydrogen generation, and in case the present voltage is equalto or greater than the fully-charged voltage, then on/off time of switch530 is changed to stop hydrogen generation. It is assumed that thisswitching operation is made by a switch control signal enabling theswitch controller 710 to set on/off time of the switch 530.

Here, the rechargeable battery 700 may be a super capacitor or a smallrechargeable battery. Super capacitor has the enhanced electriccapacity, and can charge and discharge the electric power if necessary.

FIG. 8 is a graph of the amount of hydrogen generation, expressed inunits of flow rate, when the switch is turned on.

If the switch 530 stays on for a while, the reaction becomes very fastat the beginning, raising the temperature and rapidly increasing theamount of hydrogen generation as much as 100 ml/min. Then, the amount ofhydrogen generation quickly drops due to the reduction of water in theaqueous electrolyte solution and the metal composing the first electrode220.

In such a case, it becomes difficult to control the amount of hydrogengeneration, and thus the amount of hydrogen generation is controlled toa desired flow rate by having the switch controller 520 control theturning on/off of the switch 530 such that the switch 530 has a certainduty ratio and/or on/off frequency. This will be further described withreference to FIG. 9.

FIG. 9 is a first example of the on/off frequency of the switch of ahydrogen generating apparatus in accordance with an embodiment of thepresent invention, and FIG. 10 is a second example of the on/offfrequency of the switch of a hydrogen generating apparatus in accordancewith an embodiment of the present invention. Furthermore, FIG. 11 showshow the amount of hydrogen generation is related to time when the on/offfrequency of the switch is controlled. It will be assumed hereinafterthat the switch 530 is turned on when the size of an inputted switchcontrol signal is M (i.e., high) and turned off when the size of aninputted switch control signal is 0 (i.e., low).

Referring to FIG. 9, the switch control signal inputted to the switch530 has a frequency of T and a duty ratio of 50%. In other words, theswitch control signal inputted to the switch 530 is high for ½ T and lowfor ½ T.

Referring to FIG. 10, on the other hand, the switch control signalinputted to the switch 530 has a frequency of ¼ T and a duty ratio of50%. In other words, the switch control signal inputted to the switch530 is high for ⅛ T and low for ⅛ T.

The switch control signal inputted to the switch 530 has a duty ratio(e.g., 50% in the case of FIGS. 9 and 10), and thus the switch 530 isturned on and off for the same duration within one cycle.

Referring to FIG. 11, when the duty ratio of the switch 530 iscontrolled such that 42 ml/min of hydrogen is generated for a fuel cellthat requires 2 W of electric power, there is fluctuation in the amountof hydrogen generation according to the on/off frequency. Thetemperature 1110 of the hydrogen generating apparatus 200 increasessteadily but stays below 80° C.

The amount of hydrogen generation 1120 is close to 42 ml/min. When theon/off frequency is relatively small (i.e., a large cycle) as in FIG. 9,the fluctuation is strong, as shown in boxes represented by 1140. Whenthe on/off frequency is relatively large (i.e., a small cycle) as inFIG. 10, the fluctuation is weak, as shown in boxes represented by 1150.

Therefore, for the same duty ratio, a relatively larger on/off frequencyof the switch control signal causes less fluctuation and is easier tomaintain the desired amount of hydrogen generation.

FIG. 12 is a first example of duty ratios of the switch of a hydrogengenerating apparatus in accordance with an embodiment of the presentinvention, and FIG. 13 is a second example of duty ratios of the switchof a hydrogen generating apparatus in accordance with an embodiment ofthe present invention. FIG. 14 shows how the quantity of hydrogengeneration is related to time when the duty ratio of the switch iscontrolled.

Referring to FIG. 12, the switch control signal has a cycle of T and aduty ratio of 75%, that is, the switch control signal is high for ¾ Tand low for ¼ T.

Referring to FIG. 13, the switch control signal has a cycle of T, whichis the same as that of FIG. 12, and a duty ratio of 25%, that is, theswitch control signal is high for ¼ T and low for ¾ T.

By controlling the duty ratio of the switch control signal that isinputted to the switch 530, it becomes possible to control the amount ofhydrogen generation per time that is generated in the hydrogengenerating apparatus 200.

Referring to FIG. 14, the amount of hydrogen generation is left toincrease naturally at the beginning (refer to the portion of graphrepresented by 1420), and then the switch controller 520 controls the onand off of the switch 530 to generate 42 ml/min (1421), 10 ml/min(1422), 42 ml/min (1423), 20 ml/min (1424) and 30 ml/min (1425) ofhydrogen.

When the amount of hydrogen generation is adjusted from 42 ml/min (1421)to 10 ml/min (1422), the ratio of off-time of the switch control signalwithin one cycle is increased, that is, the duty ratio is graduallydecreased. Then, by steadily maintaining the duty ratio when the flowrate meter 510 reads 10 ml/min of hydrogen generation, the amount ofhydrogen generation is kept at 10 ml/min.

When the amount of hydrogen generation is adjusted from 10 ml/min (1422)to 42 ml/min (1423), the ratio of on-time of the switch control signalwithin one cycle is increased, that is, the duty ratio is graduallyincreased. Then, by steadily maintaining the duty ratio when the flowrate meter 510 reads 42 ml/min of hydrogen generation, the amount ofhydrogen generation is kept at 42 ml/min.

By repeatedly performing the above adjustment of duty ratio, the switchcontroller 520 can adjust the amount of hydrogen generation according tochanging set values.

As described with reference to FIGS. 9 to 11, it is possible to controlthe fluctuation in the amount of hydrogen generation by changing theon/off frequency of the switch 530 in case a certain amount of hydrogengeneration is maintained.

Moreover, the amount of hydrogen generation measured in units of flowrate in FIGS. 8, 11 and 14 may be the amount of electric power outputtedfrom the fuel cell 100 in a hydrogen generating apparatus 200 shown inFIG. 7. For example, the flow rate of 42 ml/min shown in FIGS. 8, 11 and14 can correspond to 2 W, depending on the operation condition of thefuel cell 100.

In other words, the earlier-measured amounts of hydrogen generationcorrespond to the output of the fuel cell (i.e., electric power orvoltage) that is measured by the switch controller 610, 710 as shown inFIG. 6 or 7. The amount of hydrogen generation to be controlled throughthe on/off control of the switch corresponds to the output of the fuelcell, that is, electric power or voltage.

The switch of the hydrogen generating apparatus in accordance with anembodiment of the present invention can be made of an MOS (metal-oxidesemiconductor) transistor.

The switch controller of the hydrogen generating apparatus in accordancewith an embodiment of the present invention can use a power circuit ofthe fuel cell and be included in a control unit of a fuel cell powergeneration system. In other words, by including the switch controller inthe control unit of a fuel cell power generation system, the switchcontroller and the control unit of the fuel cell power generation systemcan be made into one chip.

Moreover, the hydrogen generating apparatus of the present invention cancompose a fuel cell power generation system by being connected to a fuelcell. The fuel cell power generation system includes a hydrogengenerating apparatus that is possible to control the amount of hydrogengeneration and a fuel cell that generates electricity by being suppliedwith hydrogen from the hydrogen generating apparatus.

FIG. 15 is a flowchart showing a method of controlling the amount ofhydrogen generation in a hydrogen generating apparatus in accordancewith an embodiment of the present invention. The hydrogen generatingapparatus of FIG. 15 is illustrated in FIG. 5.

The switch controller 520 of the hydrogen generating apparatus 200 turnson the switch 530 and generates hydrogen over a certain threshold offlow rate, in the step represented by S1500.

In step S1510, the flow rate meter 510 measures the amount of hydrogengeneration, and in step S1520 the switch controller 520 compares theamount of hydrogen generation, measured by the flow rate meter 510, withan inputted set value. Here, the inputted set value can be one value, asshown in step S1520 a, or have an upper limit and a lower limit with arange, as shown in step 1520 b.

The switch controller 520 generates a switch control signal forcontrolling the on/off of the switch according to the set value andapplies the switch control signal to the switch 530.

If one set value is inputted, as shown in step S1520 a, the amount ofhydrogen generation (A) and the set value (B) are compared in step S1530a. In case the amount of hydrogen generation is smaller than the setvalue (A<B), the duty ratio of the switch control signal is increased instep S1532 a, and if the amount of hydrogen generation is greater thanthe set value (A>B), the duty ratio of the switch control signal isreduced in step S1534 a. If the amount of hydrogen generation is equalto the set value (A=B), the current duty ratio of the switch controlsignal is maintained, in step S1536 a.

In case the upper limit and the lower limit are inputted in step S1520b, the amount of hydrogen generation (A), the upper limit (B1) and thelower limit (B2) are compared in step S1530 b. If the amount of hydrogengeneration is smaller than the lower limit (A<B2), the duty ratio of theswitch control signal is increased in step S1532 b, and if the amount ofhydrogen generation is greater than the upper limit (A>B1), the dutyratio of the switch control signal is reduced in step S1534 b. If theamount of hydrogen generation is between the upper limit and the lowerlimit (B2≦A≦B1), the current duty ratio of the switch control signal ismaintained in S1536 b.

By repeating steps S1520 to S1536 a or S1536 b, the hydrogen generatingapparatus 200 can generate the amount of hydrogen according to theinputted set value.

FIG. 16 is a flowchart showing a method of controlling the amount ofhydrogen generation in a hydrogen generating apparatus in accordancewith another embodiment of the present invention. The hydrogengenerating apparatus of FIG. 16 is illustrated in FIG. 6.

The switch controller 610 of the hydrogen generating apparatus 200 turnson the switch 530 and generates hydrogen over a certain threshold offlow rate, in the step represented by S1600.

The switch controller 610 measures output of fuel cell connected to thehydrogen generating apparatus 200, and receives the demanded power ofload 620 connected to the fuel cell 100, in the step represented byS1610. Here, the output of fuel cell 100 may be one of electric power orvoltage, and in case of voltage, electric power can be calculated by theuse of resistance.

And, the switch controller 610 compares the electric power C of fuelcell 100 with the demanded power D of load 620 at step S1620.

According to the comparison, in case the electric power of fuel cell 100is greater than the demanded power (C>D), the duty ratio of switchcontrol signal is reduced at step S1630, in case the electric power offuel cell 100 is smaller than the demanded power (C<D), the duty ratioof switch control signal is increased at step S1632, and in case theelectric power of fuel cell 100 is equal to the demanded power (C=D),the duty ratio of switch control signal is maintained at step S1634.Here, “equal to” means that the electric power of fuel cell 100 fallswithin the predetermined error range based on the demanded power.

Then, by repeating steps S1610 to S1630, S1632 or S1634, the hydrogengenerating apparatus 200 can control the amount of hydrogen generationfor the fuel cell to provide output corresponding to the demanded powerof load.

FIG. 17 is a flowchart of a method of controlling the quantity ofhydrogen generation in a hydrogen generating apparatus in accordancewith another embodiment of the present invention. The hydrogengenerating apparatus of FIG. 17 is illustrated in FIG. 7.

By turning on the switch 530 to generate hydrogen over a certainthreshold of flow rate, the switch controller 710 of the hydrogengenerating apparatus 200 operates the fuel cell 100 and charges therechargeable battery 700 being connected between the fuel cell 100 andthe load 620 in the step represented by S1700.

The switch controller 710 measures the voltage of rechargeable battery700 at step S1710, and compares the fully-charged voltage F of therechargeable battery 700 with the present voltage E at step S1720.

According to the comparison, in case the present voltage is equal to orgreater than the fully-charged voltage (E≧F), the switch controller 710minimizes the duty ratio of switch control signal (including 0%) toprevent the rechargeable battery 700 from being charged at step S1730,and in case the present voltage is smaller than the fully-chargedvoltage (E<F), the switch controller 710 increases the duty ratio ofswitch control signal at step S1732. Here, “equal to” means that thepresent voltage falls within the predetermined error range based on thefully-charged voltage.

Then, by repeating steps S1710 to S1730, or S1732 the hydrogengenerating apparatus 200 can control the rechargeable battery 700 to befully charged for being prepared to the peak power demanded from theload 620.

In the above method of controlling the amount of hydrogen generation,steps S1520 to S1536 a or S1536 b, or steps S1620 to S1630 or S1632, orsteps S1720 to S1730 or S1732 can be written in a computer program.Codes and code segments, composing the program, can be easily realizedby a computer programmer skilled in the art. Moreover, the program isstored in a computer readable medium, and realizes the method ofcontrolling the amount of hydrogen generation by being read and run by acomputer. The computer readable medium described above includes amagnetic recording medium, an optical recording medium and a carrierwave medium.

The drawings and detailed description are only examples of the presentinvention, serve only for describing the present invention and by nomeans limit or restrict the spirit and scope of the present invention.Thus, any person of ordinary skill in the art shall understand that alarge number of permutations and other equivalent embodiments arepossible. The true scope of the present invention must be defined onlyby the ideas of the appended claims.

What is claimed is:
 1. A hydrogen generating apparatus comprising: anelectrolyzer, filled with an aqueous electrolyte solution; a firstelectrode, accommodated in the electrolyzer, submerged in the aqueouselectrolyte solution, and generating electrons; a second electrode,accommodated in the electrolyzer, submerged in the aqueous electrolytesolution, receiving the electrons to generate hydrogen; a switch,located between the first electrode and the second electrode; a flowrate meter, measuring an amount of hydrogen generation in the secondelectrode; and a switch controller, receiving a set value, comparing theamount of hydrogen generation measured by the flow rate meter with theset value, and controlling an on/off status of the switch, wherein theswitch controller generates and outputs a switch control signal turningthe switch on and off, and wherein the switch controller is programmedto determine an on/off ratio of the switch within one cycle by varying aduty ratio of the switch control signal, control a fluctuation in theamount of hydrogen generation by varying an on/off frequency of theswitch control signal, compare the set value with the measured amount ofhydrogen generation, increase the duty ratio if the amount of hydrogengeneration is smaller than the set value, reduce the duty ratio if theamount of hydrogen generation is greater than the set value, andmaintain the duty ratio if the amount of hydrogen generation is equal tothe set value.
 2. The apparatus of claim 1, in which the switchcontroller is inputted with the set value directly from a user throughan input device.
 3. The apparatus of claim 1, in which the hydrogengenerating apparatus is coupled to a fuel cell and supplies hydrogen,and the switch controller is inputted with the set value in accordancewith an amount of hydrogen generation that is required by the fuel cell.4. The apparatus of claim 1, in which a metal forming the firstelectrode has a higher ionization tendency than a metal forming thesecond electrode.
 5. The apparatus of claim 1, in which the flow ratemeter measures the amount of hydrogen generation in units of flowrate.6. The apparatus of claim 1, in which the set value comprises an upperlimit and a lower limit, and the switch controller compares the setvalue with the measured amount of hydrogen generation, and increase theduty ratio if the amount of hydrogen generation is smaller than thelower limit, reduce the duty ratio if the amount of hydrogen generationis greater than the upper limit, and maintain the duty ratio if theamount of hydrogen generation is between the lower limit and the upperlimit.